Finite-Element and Analytical Calculations of No-Load Core Losses in Energy-Saving Induction Motors

Abstract

This paper presents a no-load core loss analysis of a three-phase energy-saving small-size induction motor supplied by a sinusoidal voltage. In the field-circuit approach, the distribution and changes of magnetic flux density in the motor are computed using a time-stepping finite-element method. The discrete Fourier transform is used to analyze the magnetic flux density waveforms in each element of the motor model. The rotational aspect of the field is included by introducing a correction to the losses generated by the first harmonic of magnetic flux density. The core losses in each element are evaluated using a loss curve measured on a toroidal core at different frequencies. Finally, an approximate analytical formulation is derived for rapid field computation. The results are compared with measurements.